System and method for tissue ablation

Abstract

A tissue ablation device comprises first and second electrodes of opposite polarities, the first electrode being mounted to a first elongated member for movement relative to the second electrode for separation therefrom by a desired distance. A method of ablating a tissue comprises inserting first and second electrodes to desired initial positions relative to a tissue mass to be ablated and applying electrical energy to the first and second electrodes to ablate a first portion of tissue between the first and second electrodes in combination with the step of applying electrical energy to desired second positions separated from the desired initial positions by a distance selected to transfer electrical energy around the first portion of tissue through a second portion of tissue to be ablated, the second portion of tissue surrounding the first portion of tissue.

1. A method of ablating tissue, comprising:
 inserting a probe having distal tissue-penetrating tip into a tissue mass to be ablated, the probe carrying, first, second, third, and fourth electrodes along a length of the probe adjacent to the tissue-penetrating tip, each separated from adjacent electrodes by respective insulators, wherein the second and third electrodes comprise center electrodes and the first and fourth electrodes comprise outer electrodes; 
 applying electrical energy to the second and third electrodes to ablate a first portion of tissue between the second and third electrodes; and 
 applying electrical energy to the first and fourth electrodes, wherein the electrical energy is conveyed around the ablated first portion of tissue through a second portion of tissue surrounding the ablated first portion of tissue, thereby ablating the second portion of tissue. 
 
     
     
       2. The method of  claim 1 , wherein relative positions between the first electrode, second electrode, third electrode, and fourth electrode are not changed when the first and second portions are ablated. 
     
     
       3. The method of  claim 1 , wherein the first electrode, second electrode, third electrode, and fourth electrode are formed on an outer surface of the probe. 
     
     
       4. The method of  claim 1 , further comprising measuring an impedance of tissue to determine when a desired degree of ablation has been achieved. 
     
     
       5. The method of  claim 4 , further comprising terminating the application of electrical energy to the first portion of tissue when the impedance thereof exceeds a first predetermined value. 
     
     
       6. A method of ablating tissue, comprising:
 inserting first and second electrodes to desired initial positions relative to a tissue mass to be ablated; 
 moving the first and second electrodes toward one another to compress a first portion of tissue; 
 applying electrical energy to the first and second electrodes to ablate the first portion of tissue between the first and second electrodes; 
 moving both the first and second electrodes to desired second positions to substantially center the ablated first portion of tissue therebetween; and 
 applying electrical energy to the first and second electrodes to convey electrical energy around the first portion of tissue through a second portion of tissue surrounding the ablated first portion of tissue, thereby ablating the second portion of tissue. 
 
     
     
       7. The method of  claim 6 , wherein one of the first and second electrodes comprises an array of tines. 
     
     
       8. The method of  claim 6 , further comprising measuring an impedance of tissue to determine when a desired degree of ablation has been achieved. 
     
     
       9. The method of  claim 8 , further comprising terminating the application of electrical energy to the first portion of tissue when the impedance thereof exceeds a first predetermined value. 
     
     
       10. A method of ablating tissue, comprising:
 inserting first and second electrodes to desired initial positions relative to a tissue mass to be ablated, wherein the first and second electrodes each comprise an array of tines; 
 moving the first and second electrodes toward one another to compress a first portion of tissue; 
 applying electrical energy to the first and second electrodes to ablate a first portion of tissue between the first and second electrodes; and 
 applying electrical energy to desired second positions separated from the desired initial positions by a distance selected to convey electrical energy around the first portion of tissue through a second portion of tissue surrounding the ablated first portion of tissue, thereby ablating the second portion of tissue. 
 
     
     
       11. The method of  claim 10 , further comprising, after ablating the first portion of tissue, moving the first and second electrodes to the desired second positions, wherein the electrical energy is applied to the first and second electrodes at the desired second positions. 
     
     
       12. The method of  claim 10 , further comprising measuring an impedance of tissue to determine when a desired degree of ablation has been achieved. 
     
     
       13. The method of  claim 12 , further comprising terminating the application of electrical energy to the first portion of tissue when the impedance thereof exceeds a first predetermined value. 
     
     
       14. A method of ablating tissue, comprising:
 inserting a first electrode array and a second electrode array into a tissue mass to be ablated; 
 moving the first electrode array and the second electrode array toward one another to compress the tissue mass; 
 applying electrical energy to the first electrode array and the second electrode array to ablate a first portion of tissue; 
 moving the first electrode array and the second electrode array away from one another to apply an expansive force to the tissue mass; and 
 applying electrical energy to the first electrode array and the second electrode array to convey electrical energy around the first portion of tissue through a second portion of tissue surrounding the ablated first portion of tissue, thereby ablating the second portion of tissue. 
 
     
     
       15. The method of  claim 14 , further comprising measuring an impedance of tissue to determine when a desired degree of ablation has been achieved. 
     
     
       16. The method of  claim 15 , further comprising terminating the application of electrical energy to the first portion of tissue when the impedance thereof exceeds a first predetermined value.